onload = function(){
	// 1. 获取动画元素
	var animateElements = Array.from(document.getElementsByClassName('animation-item'));
	var win_height = window.innerHeight;
	var offset = 0;
	var locations = [];
	animateElements.forEach(function(item,index){
		var location = item.offsetTop;
		locations.push(location);
	});
	onscroll = function(e){

		offset = document.body.scrollTop || document.documentElement.scrollTop;
		animateElements.forEach(function(item){
			if(offset + win_height >= item.offsetTop+200){
				item.classList.add('running');
			};
		});
		
	}
	
}